Can't believe I'm posting a rangemaster question

[m_charles]

So after building a bunch of different projects, of varying degrees of difficulty, a friend asks if I can make a rangemaster for him.
I confidently roll my eyes, "yes, that's sooo easy".
I happen to have a couple descent germaniums around and do the leakage tests etc and they all are well within useable leakage and gain. also, bias the resistors via the RG method in his RM build PDF.
Build up the pedal... Here's the problem: when the pedal is dimed, there is that yucky "rumble" that can happen with germs sometimes.
I've had it happen with a fuzz face and the culprit ended up being a cold solder joint on the emitter.
So I do all the usual checks, all good. Collector voltage 7.2v, all good. Sounds pretty good.
But can't kill the rumble. 
Finally, swap out the transistor. Same thing.
Since the circuit is so simple, rather than spend a ton of time trouble shooting, I pull the circuit, start over, fresh caps, resistors, same results.
So my question is: is that low unstable rumbling sound just inherant to the design of this unit? Since I don't have an original RM to compare it to, I'm kinda flying blind so to speak.
Since I've built it twice, I'm pretty sure I've covered the variables.
Also, after I clipped out the first transistor, I retested, and it was a-ok. No probs.
thx in advance for any help.
-c

[pappasmurfsharem]

So after building a bunch of different projects, of varying degrees of difficulty, a friend asks if I can make a rangemaster for him.
I confidently roll my eyes, "yes, that's sooo easy".
I happen to have a couple descent germaniums around and do the leakage tests etc and they all are well within useable leakage and gain. also, bias the resistors via the RG method in his RM build PDF.
Build up the pedal... Here's the problem: when the pedal is dimed, there is that yucky "rumble" that can happen with germs sometimes.
I've had it happen with a fuzz face and the culprit ended up being a cold solder joint on the emitter.
So I do all the usual checks, all good. Collector voltage 7.2v, all good. Sounds pretty good.
But can't kill the rumble. 
Finally, swap out the transistor. Same thing.
Since the circuit is so simple, rather than spend a ton of time trouble shooting, I pull the circuit, start over, fresh caps, resistors, same results.
So my question is: is that low unstable rumbling sound just inherant to the design of this unit? Since I don't have an original RM to compare it to, I'm kinda flying blind so to speak.
Since I've built it twice, I'm pretty sure I've covered the variables.
Also, after I clipped out the first transistor, I retested, and it was a-ok. No probs.
thx in advance for any help.
-c

Clipped out?

Why not use sockets?

[davent]

If it sounds fine up until the last little bit of pot travel why not just put a small resistor (DUT) between so it can never be dimed? Right now i'm not sure whether between the collector and pot or the power rail and pot.

edit;Seem to always have a breadboarded Rangemaster so when dimed the pot is shorted from collector to wiper so some small resistor between the pot and collector prevents the short and should prevent the rumble.

Do people run their Rangemasters wide open, on any i've built there's a huge jump in volume between bypassed and engaged long before the Rangemaster is full up.

dave

[m_charles]

The rumble is a constant, but only super-audible high up. The resistor is an idea, but kind of a band-aid IMO.
Also would cut the output.
As far as I know, the true Rangemaster is generally dimed.
Most do the mod nowadays that turns it into a full booster, but as far as I know, to truly use it as a treble boost, you keep the .0047-.0068uf in-cap blast the amp, and set the amp around that tone.
Rumor is, that's what tony iommy (sp?) did, Rory, etc... So used in that setting, it's never turned on as a boost.
So, I know all that about the pedal, but not if the rumble is normal. Ha, ha.
Anyone care to plug in their's and see if they get similar results?

[Gus]

Are you using a battery?
Do you have a power supply bypass cap?

Can you define rumble better?

Sockets do not belong in an effect that is used on stage and travels in cars and trucks etc. The transistor or IC or other part will fall out, might be on stage when you depress the switch.

[m_charles]

I'm starting to think its probably not normal, because if I have to describe it, it kinda tells me others aren't experiencing it.
😟
It's pretty much all I can think of to describe it. It's almost like if you took the static sound in-between two AM radio stations, and dropped it down an octave. It's not a "clean" white noise sound, and there's no fizz and pop like a bad trannie.
Just an unsteady rumble underneath.
Just to reiterate, pedal functions fine otherwise.
God, I'd kill to have an original just for an hour to A/B.
Hope that kinda puts the sound in your mind for an example.
Thx man

[R.G.]

It's not normal. The original does not do it. Back when I was researching the Rangemaster, a fellow sent me one to test.

What you describe is an oddity that may be an issue with the specific germanium you have not holding up well when it's turned nearly off - that is, output voltage is as high as it can be - and letting some current through.

The real answer to this question is to put an oscilloscope on it and see which of several issues it may be having. It could be situationally noisy or leaky. It could be breaking into some kind of oscillation. It *could* be a resistor, cap or solder joint with a tiny, tiny crack. If you can't scope it, replace the transistor - if you can. Otherwise, you're down to easter-egging in parts to see if something fixes it.

There are reasons that the electronics industry quit using germanium. Inconsistency was one of them.

[m_charles]

Thx RG. That was my first thought, but after clipping it out, I retested for leakage, all good, 96hfe (after acct for leakage)
Then tried another, same thing.
However, my guess is that you are correct and it's another component being finicky although there's not many to check on this build!
BTW, such a weird setup on the output. Out cap after the pot, #1 lug to 9v etc.
Maybe I will dust off my giant old scope and give a go. Just to learn something. :-)
BTW #2. All tests were done with a batt only.
Thx

[Arcane Analog]

Why not use sockets?

Most likely due to the fact that sockets lose tension (especially if there is any amount of swapping) and the device will eventually fall out. I love having expensive "boutique" pedals land on my bench only to find out the builder used sockets and their transistors are falling out.

[Arcane Analog]

I have built many Rangemasters and I have never heard a "rumble" on any setting.

[R.G.]

I love having expensive "boutique" pedals land on my bench only to find out the builder used sockets and their transistors are falling out.

Don't you wish you could get an expensive boutique pedal MAKER on your bench so you could repair THEM?   

[m_charles]

This was all done on a 6 lug terminal strip. No sockets on there.
I have used IC sockets in the past without issue, but transistor sockets can be dodgy.
This will be an easy fix when I get back to it I'm sure. Main reason for the post was after the second go, and second transistor, I wondered if I was trying to fix something that didn't need fixing.
Will report back.
Germaniums... Can be a painus in the a#%s

[Arcane Analog]

I love having expensive "boutique" pedals land on my bench only to find out the builder used sockets and their transistors are falling out.

Don't you wish you could get an expensive boutique pedal MAKER on your bench so you could repair THEM?   

Not really. I much prefer to build than repair.

[greaser_au]

I have used IC sockets in the past without issue, but transistor sockets can be dodgy.

If you have concerns about ICs coming out of sockets, a loop of thin glass reinforced nylon/vinyl cable lacing tie cord (and a little practice with knots)  is the way to go...

david